Application of a non-adiabatic tapered fiber optic biosensor for real-time, label-free detection of methyl-parathion pesticide (MPT) in presence of acetylthiocholine iodide (ATCh) is presented. The limit of detection of MPT in the presence of 1 mM ATCh as an enzyme substrate is found to be as low as $23\times 10\,\,^{-{9}}$ M (S/N=3). The proposed sensor shows a dynamic range of 2.3 nm and a working range of 0.12 to $31~\mu \text{M}$ . More importantly, it has the capability of quantifying the binding constants of MPT to the enzyme acetylcholinesterase (AChE) by performing just a single experiment. This can be done through the kinetic analysis of the analyte-enzyme reaction in the presence/absence of ATCh. The results show an association rate of $3.835\times 10\,\,^{{4}}\,\,\text{M}^{-{1}}\text{s}^{-{1}}$ and a dissociation rate of 0.2745 s⁻¹ for MPT-AChE binding in presence of ATCh which lead to a value of $1.4\times 10\,\,^{{5}}\,\,\text{M}^{-{1}}$ for equilibrium binding constant and $7.16~\mu \text{M}$ for dissociation constant. Detection of MPT in the tap and river water at low levels has been achieved and the sensor specificity examined against different substances. Based on the obtained results, our biosensor can pave the way toward low-cost, real-time, label-free, and quantitative determination of organophosphate pesticides in real samples.

中文翻译：

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使用锥形光纤生物传感器定量分析酶底物存在的甲基对硫磷农药

介绍了非绝热锥形光纤生物传感器在乙酰硫代胆碱碘化物 (ATCh) 存在下实时、无标记检测甲基对硫磷农药 (MPT) 的应用。发现存在 1 mM ATCh 作为酶底物时 MPT 的检测限低至 $23\times 10\,\,^{-{9}}$ M (S/N=3)。所提出的传感器显示动态范围为 2.3 nm，工作范围为 0.12 至 $31~\mu \text{M}$ . 更重要的是，它能够通过一次实验来量化 MPT 与乙酰胆碱酯酶 (AChE) 的结合常数。这可以通过在存在/不存在 ATCh 的情况下对分析物-酶反应进行动力学分析来完成。结果显示关联率为 $3.835\times 10\,\,^{{4}}\,\,\text{M}^{-{1}}\text{s}^{-{1}}$ 在 ATCh 存在下，MPT-AChE 结合的解离率为 0.2745 s ^-1，导致值为 $1.4\times 10\,\,^{{5}}\,\,\text{M}^{-{1}}$ 对于平衡结合常数和 $7.16~\mu \text{M}$ 为解离常数。已实现对自来水和河水中低浓度 MPT 的检测，并针对不同物质检查了传感器的特异性。基于获得的结果，我们的生物传感器可以为低成本、实时、无标记和定量测定实际样品中的有机磷农药铺平道路。